U.S. Pat. No. 5,549,382 describes a cooking hob provided with a support plate having with several cooking areas, in each of which a cooking vessel can be supported. The hob includes heating means associated with each cooking area and driving means aligned with one of the cooking areas. The driving means comprise a motor which rotates a lower magnetic coupling member located below the support plate in a position close enough to it to magnetically transmit torque to an upper magnetic coupling member attached to a stirrer located inside a cooking vessel placed on the corresponding cooking area.
Document DE-A-1131372 discloses a cooking hob comprising magnetic coupling between a lower magnetic coupling member rotatably driven by a motorised driving device and an upper magnetic coupling member connected to rotary blades or paddles installed inside a vessel. The magnetic coupling is established through a support plate on which the vessel rests.
Patent application DE-A-102006052475 discloses a cooking hob provided with a glass, glass ceramic or the like support plate with several cooking areas associated with heating means, where one of the cooking areas includes a lower magnetic coupling member rotatably driven by a motor to establish magnetic coupling through the support plate with an upper magnetic coupling member attached to a stirrer located inside a vessel placed on one of the cooking areas to rotate the stirrer inside the vessel.
A drawback of these cooking hobs equipped with a substantially smooth support plate and driving means to rotate a lower magnetic element and thereby establish magnetic coupling through the support plate is that if for any reason the rotary blades or paddles increase resistance to rotation or are locked inside the vessel, for example due to the conditions of the food being processed, then the entire vessel tends to rotate on the support plate being pushed by the driving means with the risk of ruining the culinary preparation inside the vessel, scratching the support plate or even causing an accident.
Documents DE-A-3000593, DE-A-3836099, EP-A-0725556, WO-A-9631739, U.S. Pat. No. 4,587,406 describe different wireless communication systems for communicating between a cooking vessel and a cooking hob provided with a cooking area with electric heating means on which the vessel is placed for the purpose of transmitting data relating to the cooking conditions, especially the temperature in the vessel, and controlling the electric heating means according to the data received from the vessel by means of a control device.
An advantage of the cooking hobs provided with a continuous glass, glass ceramic or the like support plate is that the support plate has a very easy to clean smooth and completely cleared upper surface. Nevertheless, this smooth and cleared surface offers very little resistance to the rotation of the vessel. Accordingly, there is a need to provide means preventing the rotation of the vessel on the plate and means preventing the operation of the driving means if the vessel is not placed on the treatment area of the support plate in a predetermined angular position.